Control device



June 15, 1943. w. A. RAY 2,321,852

CONTROL DEVICE Filed June 25, 1941 Jig 3nventor,

MAL/AM A. 84K

(Ittdmeg provide a unite Patented June 15, 1943 UNITED STATES PATENT OFFICE CONTROL DEVICE William A. Ray, Glendale, Calif.

Application June 25, 1941, Serial No. 399,600

Claims.

My present invention relatesto control devices and particularly to those of the thermally responsive type. It is well known that, in a space wherein fluid is circulating, the distribution of heat is never uniform. Not only is the temperature at various points in the space difierent, but also the temperature difference between the points may vary considerably with variation of fluid circulation. Thus, when a plurality of thermally responsive devices, the settings of which should be proportional, are located at various points, their respective responses under varying conditions of fluid irculation will vary. ihis "efiect is particularly noticeable in the bonnet of a hot-air furnace wherein the distribution of heat is greatly aiiected by the opening or closing of the hot-air ducts and by change of circalation in the spaces heated by the furnace. It therefore a general. object of my invention to temperature control device comoris a plurality of thermally responsive elemems Wh."'-h are so intimately arranged with respe t to each other that the temperature of the va ious elements is aavays substantially the same.

Another object of. my invention is the provision of a control device, particularly adapted for use in the bonnet of a hot-air furnace, which com-= prises a pair of elongated thermally responsive elements, one of which encircles a substantial portion of the ci Another object is the provision of a control device of the type indicated in the preceding object wherein one of the thermally responsive elements is of metal (bimetal or expansion-rod type) and the other of the fluid-expansion type which, while not as permanently reliable as the metallic typeon'account of possible eventual.

Figure 2 is a diagrammatic view of a hot-air heating system including the device shown in Fig. 1.

Referring first to Fig. 1 of the drawing, the numeral I l indicates a casing or base member having a flange, l2 for attachment to the wall of a heating device. The central portion of the vertical wall of the casing is thickened to provide a boss [3, to a reduced outer portion of which is secured one end of a spirally-wound bimetallic strip M. The other or outer end of the bimetallic strip is secured to a centrally located rod IS, the innerend portion of which extends through and is guided in an opening in the boss l3 and easing Wall. To the end of rod within the casing is secured a cam l5, upon the surface of which one end of a flexible metallic contact strip ll constantly bears, the other end of the strip being secured to a terminal it insulatingly mounted in the upper wall of the casing. Con acted a similar terminal is another contact strip 28, the bent lower end of which is normally in engagernent with con act strip i'i.

Sealingly mounted in a passage 2; i the E3 is the inner open end a spirally-wound bular member or coil 22 which encircles stantial portion or" the bimetallic member The sealed outer end of the coil is supporte K bracket 23 attached to a perforated :ylinc. guard housing 2d carried by the boss 53. The passage El communicates with a recess in the underside of the thickened bottom wall of the casing, covering which recess is a flexible diaphragm 28, secured at its margin to undersuriace of the casing by a housing 2?. The tubular member 22 and the recess 25 are charged with a thermaliy-expansibie fluid; the fluid pressure system being either of the hydraulic or vapor-tension type, whichever is more suitable to the particular conditions under whichthe device is to be employed. Carried by the central portion of the diaphragm is a contact plate 28 which, when the diaphragm is forced downward by fluid pressure in the recess 25, is adapted to bridge the head of contact screws 29, insulatingly mounted in the bottom wall of housing 21; a compression spring 30 urging the diaphragm and contact plate upward. Closing the open end of casing H is a cover plate 3|.

Referring now to the diagram of Fig. 2, the numeral indicates the outer wall of a hot-air furnace which includes a central heating unit or stove 4| wherein is located a main gas burner 42. This burner is supplied with fuel by a conduit 43 wherein is connected a main valve casing 44, flow through which is controlled by 21. diaphragm-carried closure 45. Gas pressure on the diaphragm for actuating the closure is controlled by an electrically operated pilot valve, generally indicated at 46, in a manner well known in the art.

The air heated by the stove M is supplied by an electrically operated fan 41,- mounted' in an inlet duct 48, to a space or room 49 through an outlet duct 50. Outlet ducts for supplying other rooms are indicated at and 52. Mounted in the room 49 is a thermostat 53 which controls the energization of pilot valve 46 in accordance with the heating requirements of the room. This thermostat is connected by wires 54 to the pilot valve in series with terminals l8 and IS of the control device shown in Fig. 1 and a thermoelectric device 55 which is heated by the flame of a pilot burner 56 provided for the ignition of the main burner and connected to the gas supply ahead of the main burner valve. The thermoelectric device 55, preferably composed ofa plurality of thermocouples connected in series, is employed as a convenient source of power; which power is ample for the energization of pilot valve 46, and has an additional advantage in that, upon accidental-extinction of the pilot burner flame, the resultant cess'ationof currenteffects closure of the main burner "valve. The fan 41 is connected by wires 51 to any suitable source of electrical energy in series with terminals 29' of the fluid pressure operated switch of the control device shown in Fig. l.

The operation of the heating system is as fol-'- lows: When the temperature in the room falls to a point at which heat is demanded, the thermostat 53 completes the electrical circuit between,

the pilot valve 46 and the source of energy 55, the contacts l1 and actuated by the bimetallic member I! being normally closed, with the result that fuel is supplied to the main burner where it is ignited by the continuously burning flame of the pilot burner. 56 Upon suflicient rise of temperature in the furnace bonnet, the fluid in coil 22 expands, closing contacts 29, and the fan 41 is operated to circulate the heated air to the room. When the demand for heat is satisfied, the room thermostat acts to close fuel supply to the main burner, the fancontinuing to operate until the bonnet temperature reaches a low point at which the fluid pressure operated switch contacts open. In the event of abnormal rise in bonnet temperature, such as might be occasioned by the closing of one ormore of the hot-air ducts, the bimetallic coil l4 expands to such an extent that its cam isrotated to a position in which contacts I! and 20 are open. When this occurs, due'to the resultant deenergization'of pilot valve 66, fuel supply to the main burner is stopped until the bonnet temperature falls to a safe low degree.

As was pointed out in the statement of invention, .the thermally responsive elements l4 and 22 are so intimately arranged that they are always substantially at the same respective temperature and therefore maintain thenadjusted ratio of response. J If the elements were located at different points in the furnace bounce-spaced even onlyan inch or so apart.this ratio would not bemaintained with variation of furnace conditions and fluid circulation in the bonnet (caused, for example, by the opening or closin of one or more of the hot-air ducts) which would affect one element to a greater degree thanthe other. As vwas brought out above in the final reliable bimetallic or expansion-rod type of thermostat is preferred as a high-limit control.

While I have herein shown and described a specific form of my invention and its applica-.

tion to the control of a hot-air furnace, it is obvious that the device shown. is subject to modification without departing from the spirit of tho invention and is applicable to the control of other systems. Iintend therefore tobe limited only by the scope of the appended claims.

I claim as myinvention:

1. In adual device for controlling the operation of temperature changingv means: a pair of thermostatic elements adapted to be subjected to the temperature of a flowing circumambient medium, one of the elements being surrounded by the otherto form an outer a'ndan-inner element, said outer element being arranged in such manner as to p-rovide'a free'opening to the inner element, said opening being so arranged that the circumambient. medium substantially uniformly afiects the elements in any direction of flow thereof, and independent switching means actuated by each of the elements. v

2. In a dual device for controlling the operation of temperature changing means: apair of thermostatic elements adapted to be subjected to the temperature of a flowing circurnambient medium, one of said elementsbeing coiled around the other to form an inner and an outer element, the coils of said outer element being spaced apart to permit free circulation of vthe cii'cumambient medium to the innerelement so thatboth of the elements are substantially uniformly eflected by flow of the medium in any direction, and; independent switching means actuated by each of the elements.

3. In a dual device for controlling the operation of temperature changing'means: a pair of thermostatic elements adapted to be subjected to the temperature of a flowing circumambient medium. one of said elements being. in the form -of an elongated thermally expansible metallic O ject, it is preferred to employ a thermostat of 1 the fluid-expansion type forthe control of the circulating fan on account of its greater flexibillty and capability of producing more power per unit of heat-collecting area, while the more member, the other ofsaid elements being in the form of an elongated hollow member containing a thermally expansible fluid, one of the elements being surrounded by the other to form an outer and an innerelement, said outer'element being arranged in such-manner as to provide a free opening to the inner element, said opening being so arranged that the circumambient medium substantially uniformly affects the elements in any direction of flowthereof, and independent switching means actuated by each of the elements.

4. In a dual device for controlling the operationof temperature changing means: a base member, a pair of thermostatic. elements extending from said base member at one side thereof and adapted to be subjected to the tempera:

ture of a flowing medium circumambient the elements, one of said elements consisting of an elongated thermally expansible metallic member, the other of said elements consisting .of an ditional switching means also mounted on said base member and actuated 'by the expansion of 5. In a dual device for controlling the operation of temperature changing means: a base member, a pair of thermostatic elements extending from said base member at one side thereof and adapted to be subjected to the temperature of a flowing medium circumambient the elements, one of said elements consisting of an elongated thermally expansible metallic member, the other of said elements consisting of an elongated hollow member containing a thermally expansible fluid, said hollow member being coiled around said metallic member in spaced relation thereto to form an inner and an outer element,

- the coils of said outer element being spaced apart to permit free circulation of said medium to the inner element so that both of the elements are substantially uniformly affected by flow of the medium in any direction, switching means mounted on said base member and actuated by the expansion of said metallic member, and additional switching means also mounted on said base member and actuated by the expansion of said fluid.

- WILLIAM A. RAY. 

